Control system for engine

Abstract

An engine is equipped with a first injection valve that injects fuel into an intake passage, and a second injection valve that injects fuel into a cylinder. The engine is provided with a fuel supply system having a first supply path for the first injection valve and a second supply path for the second injection valve. Moreover, an electronic control unit of the engine executes a unilateral injection process for causing fuel to be injected from one of the first injection valve and the second injection valve and prohibiting fuel injection from the other injection valve, when it is determined that there is a deviation between a property of fuel in the first supply path and a property of fuel in the second supply path.

What is claimed is: 
     
       1. A control system comprising:
 an engine including
 a first injection valve and a second injection valve that are configured to supply fuel into a same cylinder of the engine, 
 a fuel supply system including
 a first supply path that is configured to supply fuel in a fuel tank to the first injection valve, and 
 a second supply path that is configured to supply fuel in the fuel tank to the second injection valve; and 
 
 
 an electronic control unit that is configured to 
 i) control fuel injection from the first injection valve and fuel injection from the second injection valve in accordance with an operating state of the engine, 
 ii) determine whether there is a deviation between a property of fuel in the first supply path and a property of fuel in the second supply path, and 
 iii) execute a unilateral injection process when the electronic control unit determines that there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path, wherein 
 the unilateral injection process is a process of causing fuel to be injected from one of the first injection valve and the second injection valve, and prohibiting fuel injection from the other injection valve. 
 
     
     
       2. The control system according to  claim 1 , wherein
 the electronic control unit is configured to execute the unilateral injection process when the electronic control unit determines that the engine is in idling operation and that there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path. 
 
     
     
       3. The control system according to  claim 1 , wherein
 the electronic control unit is configured to execute the unilateral injection process when the electronic control unit determines that a vehicle is stopped and that there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path. 
 
     
     
       4. The control system according to  claim 1 , wherein
 the electronic control unit is configured to 
 i) determine that fuel stored in the fuel supply system before a change in the property of fuel in the fuel tank is old fuel, and that fuel in the fuel tank is new fuel, when there is a deviation between the property of fuel in the fuel tank and the property of fuel stored in the fuel supply system due to the change in the property of fuel in the fuel tank, and 
 ii) cause fuel to be injected from a specific injection valve and prohibit fuel injection from the other injection valve, the other injection valve being one of the first injection valve and the second injection valve which is different from the specific injection valve, wherein 
 the specific injection valve is one of the first injection valve and the second injection valve which injects fuel in a specific supply path, and 
 the specific supply path is one of the first supply path and the second supply path in which the old fuel remains. 
 
     
     
       5. The control system according to  claim 4 , further comprising:
 a detection sensor, wherein 
 the detection sensor is provided in a common path and detects a property of fuel, 
 the common path is connected to the fuel tank, 
 upstream ends of both the first supply path and the second supply path are connected to a downstream end of the common path, and 
 the electronic control unit is configured to determine whether there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path when the property of fuel detected by the detection sensor changes. 
 
     
     
       6. The control system according to  claim 4 , wherein
 the electronic control unit is configured to calculate at least one of a first estimated value and a second estimated value, 
 the first estimated value being an estimated value of an amount of the old fuel remaining in the first supply path that is estimated based on a volume of the first supply path and an amount of fuel injection from the first injection valve, and 
 the second estimated value being an estimated value of an amount of the new fuel flowing into the first supply path, 
 the electronic control unit is configured to calculate at least one of a third estimated value and a fourth estimated value, 
 the third estimated value being an estimated value of an amount of old fuel remaining in the second supply path that is estimated based on a volume of the second supply path and an amount of fuel injection from the second injection valve, and 
 the fourth estimated value being an estimated value of an amount of new fuel flowing into the second supply path, and 
 the electronic control unit determines whether there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path, based on a calculation result of one of the calculated first estimated value and the calculated second estimated value and a calculation result of one of the calculated third estimated value and the calculated fourth estimated value. 
 
     
     
       7. The control system according to  claim 1 , wherein
 the electronic control unit is configured to 
 i) determine that fuel stored in the fuel supply system before an increase in an amount of fuel stored in the fuel tank is old fuel, and that fuel in the fuel tank is new fuel, when the amount of fuel stored in the fuel tank increases, and 
 ii) cause fuel to be injected from a specific injection valve and prohibit fuel injection from the other injection valve, the other injection valve being one of the first injection valve and the second injection valve which is different from the specific injection valve, wherein 
 the specific injection valve is one of the first injection valve and the second injection valve which injects fuel in a specific supply path, and 
 the specific supply path is one of the first supply path and the second supply path in which the old fuel remains. 
 
     
     
       8. The control system according to  claim 7 , wherein
 the electronic control unit is configured to determine whether there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path when the amount of fuel stored in the fuel tank increases. 
 
     
     
       9. The control system according to  claim 7 , wherein
 the electronic control unit is configured to calculate at least one of a first estimated value and a second estimated value, 
 the first estimated value being an estimated value of an amount of old fuel remaining in the first supply path that is estimated based on a volume of the first supply path and an amount of fuel injection from the first injection valve, and 
 the second estimated value being an estimated value of an amount of new fuel flowing into the first supply path, 
 the electronic control unit is configured to calculate at least one of a third estimated value and a fourth estimated value, 
 the third estimated value being an estimated value of an amount of old fuel remaining in the second supply path that is estimated based on a volume of the second supply path and an amount of fuel injection from the second injection valve, and 
 the fourth estimated value being an estimated value of an amount of new fuel flowing into the second supply path, and 
 the electronic control unit is configured to determine whether there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path, based on a calculation result of one of the calculated first estimated value and the calculated second estimated value and a calculation result of one of the calculated third estimated value and the calculated fourth estimated value. 
 
     
     
       10. The control system according to  claim 1 , wherein
 the electronic control unit is configured to calculate an injection sharing ratio, 
 the injection sharing ratio being a value obtained by dividing an amount of fuel injection from the first injection valve by a sum of the amount of fuel injection from the first injection valve and an amount of fuel injection from the second injection valve, and 
 the electronic control unit is configured to determine that there is a deviation between the property of fuel in the first supply path and the property of fuel in the second supply path when an air-fuel ratio of exhaust gas flowing through an exhaust passage of the engine changes due to a change in the injection sharing ratio. 
 
     
     
       11. The control system according to  claim 1 , wherein
 fuel in the engine is alcohol-containing fuel, and 
 the electronic control unit is configured to determine whether there is a deviation between a concentration of alcohol in fuel in the first supply path and a concentration of alcohol in fuel in the second supply path. 
 
     
     
       12. The control system according to  claim 1 , wherein
 the first injection valve is a valve that injects fuel into an intake passage, and 
 the second injection valve is a valve that injects fuel into the cylinder.